When to start stealing

[PoBoy321]

I'm new to playing STTs and I've been playing $10+1s on party and some of the steps. Anyway, I think that one of my biggest problems is not stealing blinds early enough. I usually wait until the 4th level (blinds 50/100) to start stealing, but lately I've found that I don't have a large enough chip stack to effectively steal by that point, so should I start stealing earlier? If so, how much earlier?